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Thermochemical sulphate reduction in the Upper Devonian Cairn Formation of the Fairholme carbonate complex (South‐West Alberta, Canadian Rockies): evidence from fluid inclusions and isotopic data
Author(s) -
VANDEGINSTE VEERLE,
SWENNEN RUDY,
GLEESON SARAH A.,
ELLAM ROB M.,
OSADETZ KIRK,
ROURE FRANÇOIS
Publication year - 2009
Publication title -
sedimentology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.494
H-Index - 108
eISSN - 1365-3091
pISSN - 0037-0746
DOI - 10.1111/j.1365-3091.2008.00978.x
Subject(s) - geology , halite , calcite , carbonate , fluid inclusions , dolomite , devonian , mineralogy , geochemistry , siliciclastic , meteoric water , quartz , dolomitization , diagenesis , dissolution , chemistry , gypsum , geomorphology , paleontology , groundwater , sedimentary depositional environment , geotechnical engineering , organic chemistry , structural basin , facies
The Fairholme carbonate complex is part of the extensively dolomitized Upper Devonian carbonate reefs in west‐central Alberta. The studied formations contain moulds (up to 10 cm in diameter), which are filled partially with (saddle) dolomite, quartz and calcite cements. These cements precipitated from a mixture of brines that acquired high salinity by dissolution of halite and brines derived from evaporated sea water. The fluids were warm (homogenization temperature of primary fluid inclusions of 76 to 200 °C) and saline (20 to 25 wt% NaCl equivalent) and testify to thermochemical sulphate reduction processes. The latter is deduced from S in solid inclusions, CO 2 and H 2 S in volatile‐rich aqueous inclusions and depleted δ 13 C values down to −26‰ Vienna Pee Dee Belemnite. High 87 Sr/ 86 Sr values (0·7094 to 0·7110) of the cements also indicate interaction of the fluids with siliciclastic sequences. The thermochemical sulphate reduction‐related cements probably formed during early Laramide burial. Another (younger) calcite phase, characterized by depleted δ 18 O values (−23·9‰ to −13·9‰ Vienna Pee Dee Belemnite), low Na (27 to 37 p.p.m.) and Sr (39 to 150 p.p.m.) concentrations and non‐saline (∼0 wt% NaCl equivalent) fluid inclusions, is attributed to post‐Laramide meteoric water.